Automatic generating device for 3-d structure shape, automatic generating method, program therefor, and recording medium recording the program

ABSTRACT

An automatic three-dimensional structure shape generation apparatus for automatically generating the shape of a three-dimensional structure from a plurality of points having three-dimensional coordinates containing height information includes means for constituting a point group by collecting points such that three-dimensional distances between the points are within a predetermined threshold or two-dimensional distances and height differences between the points are within predetermined thresholds, means for detecting a polygon that includes the points of the point group at a minimum area from at least one of a plurality of predetermined polygons, and means for generating an outer shape or a rooftop shape of the three-dimensional structure from the polygon having the minimum area.

TECHNICAL FIELD

[0001] The present invention relates to an automatic three-dimensionalstructure shape generation apparatus and an automatic three-dimensionalstructure shape generation method for automatically generating shapes ofthree-dimensional structures such as land features and buildings, whichare components of a three-dimensional map, by using informationregarding a cloud of points in a three-dimensional coordinate system,which is obtained through an apparatus (a laser profiler) or LIDAR(LIght Detection And Ranging) data for detecting height data of the landfeatures, the buildings and other objects by irradiating lasers towardthe ground from an airplane in the sky, a program thereof and arecording medium for recording the program.

BACKGROUND ART

[0002] In recent times, the marked development of informationtechnologies (IT) has promoted transition from conventional paper-basedtwo-dimensional maps to two-dimensional electronic maps, and furtherthree-dimensional electronic maps are being constructed to target a widearea such as car navigation systems and GISs (Geographic InformationSystems) using computers.

[0003] In order to construct a three-dimensional electronic map, it isnecessary to obtain height information regarding land features,buildings and other objects, which are components of thethree-dimensional electronic map. A laser profiler or LIDAR data havebeen developed and used as means for easily acquiring such heightinformation. The laser profiler irradiates lasers toward the ground froman airplane and obtains height information based on time differencesbetween the lasers reflected from the ground.

[0004] The laser profiler obtains point cloud data constituted of alarge number of three-dimensional point data including the heightinformation. In order to construct a three-dimensional electronic mapbased on the point cloud data, it is necessary to detect land featuresand three-dimensional shapes of three-dimensional structures such asouter shapes, rooftop shapes, and further roof shapes thereof.

[0005] In order to detect the land features and the three-dimensionalstructure shapes based on the point cloud data, a variety of methodshave been conventionally used. In one method, land features andthree-dimensional structure shapes such as building shapes are detectedand determined through visual observation on a computer display from theheight information of the point cloud data. In another method, the landfeatures and the three-dimensional structure shapes are detected anddetermined by using a satellite image (satellite imagery data) of theground taken from a satellite together with the height information ofthe point cloud data, and the satellite image is compared with theheight information through visual observation thereof on a computerdisplay. Then, a drawing is made by using a computer to reshape and editthe shapes of three-dimensional structures detected in accordance withthe above-mentioned methods.

[0006] The conventional methods, however, need a considerable amount ofhuman labor, and the three-dimensional structure shapes are detected anddetermined depending on skills and experiences of staff members. As aresult, the detected and determined three-dimensional structure shapeshave quality differences.

[0007] Additionally, when the conventional methods are used to constructa three-dimensional map of a city that has a large number ofthree-dimensional structures in a broad area, considerable human laborand cost are required. For instance, millions of three-dimensionalstructures are located in 23 wards of Tokyo at present. If one staffmember is assumed to be able to deal with 50 structures per a day, itwould take more than 200 years to generate all shapes of thethree-dimensional structures. Therefore, it is difficult to practicallyapply the conventional three-dimensional structure shape generationmethods to wider areas, for instance, all cities in Japan and all citiesaround the world.

DISCLOSURE OF INVENTION

[0008] It is an object of the present invention to provide an improvedautomatic three-dimensional structure shape generation apparatus, anautomatic three-dimensional structure shape generation method, a programthereof, and a recording medium for storing the program in which theabove-mentioned problems are eliminated.

[0009] A more specific object of the present invention is to provide anautomatic three-dimensional structure shape generation apparatus and anautomatic three-dimensional structure shape generation method that canautomatically generate shapes of three-dimensional structures of uniformquality at a reasonable cost, a program thereof, and a recording mediumfor storing the program.

[0010] In order to achieve the above-mentioned objects, there isprovided according to one aspect of the present invention an automaticthree-dimensional structure shape generation apparatus for automaticallygenerating a shape of a three-dimensional structure from a plurality ofpoints having three-dimensional coordinates containing heightinformation, comprising: means for constituting a point group bycollecting such points that three-dimensional distances between thepoints are within a predetermined threshold or two-dimensional distancesand height differences between the points are within predeterminedthresholds; means for detecting a polygon that includes the points ofthe point group at a minimum area from at least one of predeterminedpolygons; and means for generating an outer shape or a rooftop shape ofthe three-dimensional structure from the polygon having the minimumarea.

[0011] According to the above-mentioned invention, it is possible toautomatically generate shapes of three-dimensional structures of uniformquality with minimal use of human resources.

[0012] In the above-mentioned automatic three-dimensional structureshape generation apparatus, the means for detecting the polygon havingthe minimum area may gradually rotate all points in the point group orat least one of the predetermined polygons by a unit of a predeterminedangle so as to find an angle at which the polygon has a minimum area.

[0013] According to the above-mentioned invention, it is possible togenerate shapes of three-dimensional structures with high accuracy.

[0014] In the above-mentioned automatic three-dimensional structureshape generation apparatus, the means for detecting the polygon havingthe minimum area may detect the polygon that includes the points of thepoint group at the minimum area based on an angle at which an edge ofthe polygon that includes the point group coincides with a predetermineddirection vector.

[0015] According to the above-mentioned invention, the polygon includingthe points at the minimum area is selected without the gradual rotationof the polygons or the points under the limited direction of thethree-dimensional structure. As a result, it is possible to reduceprocessing time.

[0016] From the viewpoint of arrangement of the generated outer shape orthe generated rooftop shape of the three-dimensional structure, theabove-mentioned automatic three-dimensional structure shape generationapparatus may further comprise means for removing an overflow portion ofone of the generated outer shape and the generated rooftop shape of thethree-dimensional structure from a corresponding building shape in atwo-dimensional electronic map or means for arranging one of thegenerated outer shape and the generated rooftop shape of thethree-dimensional structure such that the generated one is included inthe corresponding building shape in the two-dimensional electronic map.

[0017] According to the above-mentioned invention, it is possible togenerate the outer shape or the rooftop shape of the three-dimensionalstructure with high accuracy.

[0018] Additionally, there is provided according to another aspect ofthe present invention, that is, an aspect of three-dimensional structureshape generation using coefficients of a predetermined function, anautomatic three-dimensional structure shape generation apparatus forautomatically generating a shape of a three-dimensional structure from aplurality of points having three-dimensional coordinates containingheight information, comprising: means for constituting a point group bycollecting such points that three-dimensional distances between thepoints are within a predetermined threshold or two-dimensional distancesand height differences between the points are within predeterminedthresholds; means for using height information z (z>0) of the points ofthe point group and a predetermined function to determine a coefficientof the function such that errors between the points and the function areminimized; and means for generating the shape of the three-dimensionalstructure based on the coefficient.

[0019] According to the above-mentioned invention, it is possible toautomatically generate the roof shapes of the three-dimensionalstructures of uniform quality with minimal use of human resources.

[0020] In the above-mentioned automatic three-dimensional structureshape generation apparatus, the means for generating the shape of thethree-dimensional structure based on the coefficient may compute atleast one coefficient of a power series function whose order is higherthan or equal to a first order or a linear combination function of anelementary function in accordance with a least square method, andgenerate a roof shape of the three-dimensional structure based on a sizerelation of the at least one coefficient.

[0021] According to the above-mentioned invention, it is possible toautomatically generate the roof shape of the three-dimensional structureof uniform quality with minimal use of human resources.

[0022] In the above-mentioned automatic three-dimensional structureshape generation apparatus, the means for generating the shape of thethree-dimensional structure based on the coefficient may extract aplurality of points, which are located at higher positions, from thepoint group, find a line or a curve such that errors between the pluralpoints located at higher positions and the line or the curve areminimized, and generate a roof shape by determining the one as a roofedge.

[0023] According to the above-mentioned invention, it is possible toautomatically generate the roof shapes of the three-dimensionalstructures of uniform quality with minimal use of human resources.

[0024] Additionally, it is possible to provide an automaticthree-dimensional structure shape generation method with the sameoperation and effect as the above-mentioned automatic three-dimensionalstructure shape generation apparatus. Also, it is possible to implementa program for causing a computer to perform a process for the automaticthree-dimensional structure shape generation.

BRIEF DESCRIPTION OF DRAWINGS

[0025] Other objects, features and advantages of the present inventionwill become more apparent from the following detailed description whenread in conjunction with the accompanying drawings.

[0026]FIG. 1 is a diagram illustrating an example of hardwareconfiguration of an automatic three-dimensional structure shapegeneration apparatus according to the present invention;

[0027]FIG. 2 is a flowchart of an algorithm for generating an outershape and a rooftop shape of a three-dimensional structure based onpoint cloud data;

[0028]FIG. 3 is a diagram illustrating a method for determiningarrangement of a polygon that includes points at a minimum area;

[0029]FIG. 4 is a flowchart of a procedure for generating the outershape and the rooftop shape of the three-dimensional structure based onthe point cloud data and a building shape in a two-dimensionalelectronic map;

[0030]FIG. 5 is a flowchart of a procedure for generating a roof shapeof a three-dimensional structure based on a point group;

[0031]FIG. 6 is a diagram illustrating roof shapes and names thereof;

[0032]FIG. 7A is a diagram illustrating an example of a point group;

[0033]FIG. 7B is a diagram illustrating an example of extraction of asubgroup of points at higher positions from the point group in FIG. 7A;

[0034] FIG. .7C is a diagram illustrating an example of a determinededge from the extracted subgroup in FIG. 7B;

[0035]FIG. 8 is a diagram illustrating an example of three-dimensionalstructures generated in accordance with the present invention;

[0036]FIG. 9 is a diagram illustrating a second example of athree-dimensional structure generated in accordance with the presentinvention;

[0037]FIG. 10A is a diagram illustrating point cloud data in a block (1km²) in Tokyo obtained by using a laser profiler; and

[0038]FIG. 10B is a diagram illustrating an example of three-dimensionalstructures automatically generated based on the point cloud data in FIG.10A.

[0039] Additionally, primary parts used in FIG. 1 through FIG. 10B are amain control unit 10, a memory device 20, point cloud data 21, polygondata 22, threshold data 23, function data 24, two-dimensional electronicdata 25, roof shape data 26, an input-output control unit 30, an inputdevice 40, a display device 50 and an output device 60.

BEST MODE FOR CARRYING OUT THE INVENTION

[0040] In the present invention, point cloud data, which are obtainedthrough a laser profiler or other apparatuses, are used to form pointgroups each of which is constituted of points. The points are grouped insuch a way that three-dimensional distances between the points arewithin a predetermined threshold or both two-dimensional distances andheight differences thereof are within predetermined thresholds. For eachpoint group, at least one prepared polygon is used to include all pointsthereof. At this time, the direction (orientation) of the polygon isdetermined as such a direction that the polygon occupies the minimumarea required to include the points, and then the minimum area ismeasured. The above measurement is conducted for all prepared polygons.The polygon having the minimum area is selected among the preparedpolygons, and an outer shape or a rooftop shape of a three-dimensionalstructure is generated based on the selected polygon.

[0041] Here, the above-mentioned three-dimensional distance between twopoints means a distance between the two points in a space prescribed bymutually orthogonal three-dimensional coordinate axes: a longitudinaldirection, a transverse direction and a vertical direction. On the otherhand, the above-mentioned two-dimensional distance between two pointsmeans a distance between the two points in a two-dimensional planeprescribed by the longitudinal and the transverse axes.

[0042] Also, the rooftop shape according to the present invention isrepresented as a polygon that is generated based on points, which arelocated at higher positions, of the point group. The rooftop shape isgenerated in accordance with the same generation method as the outershape.

[0043] There are some methods for finding the above-mentioned polygonhaving the minimum area. In one typical method, the minimum-size polygonis found by rotating point cloud data or polygons. In another typicalmethod, the direction of a building shape (direction vector) isdetermined by using a two-dimensional electronic map, and theminimum-size polygon is found in a state where one edge of the polygonis arranged to the direction. Here, the direction vector is determinedby detecting a main direction of the building shape (a south-facingdirection, a road-facing direction and so on) based on the position ofthe building in the two-dimensional electronic map and so on.

[0044] Additionally, if the generated outer shape or roof shape of thethree-dimensional structure is compared with the building shape in thetwo-dimensional electronic map, it is possible to generate thethree-dimensional structure with high accuracy by removing an overflowportion of the outer shape or the rooftop shape from the correspondingbuilding shape in the two-dimensional electronic map or shaping theouter shape or the rooftop shape such that the outer shape or therooftop shape is included in the building shape.

[0045] On the other hand, a roof shape is generated as follows. First, aheight coordinate of each point of the point group is represented as z(z>0), and at least one coefficient of a formula z=f(x, y), which isformulated as a power series function whose order is more than or equalto the first order or a linear combination function of elementaryfunctions, is found in accordance with the least squares method. Then,the roof shape of the three-dimensional structure is generated based onsizes of found coefficients.

[0046] Here, when the roof shape is generated, a plurality of pointslocated at higher positions are sampled from the point group. Then, aline (or a curve) that is located at minimum distances from the sampledpoints is found in accordance with the least squares method. If the line(or the curve) is considered as an edge of the roof, it is possible togenerate the roof shape including the edge.

[0047] In the following, embodiments of the present invention will bedescribed with reference to the accompanying drawings.

[0048]FIG. 1 shows an example of hardware configuration of an automaticthree-dimensional structure shape generation apparatus according to thepresent invention.

[0049] In FIG. 1, a memory device 20 is connected to a main control unit10 (a control unit, which is referred to as a CPU (Central ProcessingUnit) hereinafter) programmed to control the overall automaticthree-dimensional structure shape generation apparatus. The CPU 10 isconnected to an input device 40 comprised of a keyboard and a pointingdevice such as a mouse via an input control unit 30, a display device 50such as a monitor for displaying execution instruction screens, inputresults and so on, and an output device 60 for outputting generatedthree-dimensional structures. The CPU 10 contains an inner memory forstoring operating programs such as OS (Operating System), programs forprescribing procedures for generating three-dimensional structures, andnecessary data. By executing these programs, it is possible to implementthe above-mentioned process for detecting a polygon that includes pointsof a point group at a minimum area, the above-mentioned process forgenerating an outer shape or a rooftop shape of a three-dimensionalstructure from the detected polygon of the minimum area, and otherprocesses. The memory device 20 serves as a storage part for such as ahard disk, a flexible disk, an optical disk and so on. Point cloud data21, polygon data 22, threshold data 23, function data 24,two-dimensional map data 25 and roof data 26 are stored in the memorydevice 20.

[0050] A description will now be given, with reference to the hardwareconfiguration in FIG. 1, of the process for automatically generatingshapes of three-dimensional structures.

[0051]FIG. 2 is a flowchart of an algorithm for automatically generatingouter shapes and rooftop shapes of three-dimensional structures frompoint cloud data.

[0052] In FIG. 2, when the CPU 10 receives an execution instruction fromthe input device 40, the CPU 10 reads the point cloud data 21 obtainedthrough a laser profiler and others from the memory device 20 (S201).Normally, the point cloud data are represented as three-dimensionalcoordinates of several hundred thousand points per one square kilometer.Then, the CPU 10 computes three-dimensional distances of at least threepoints or both two-dimensional distances and height differences thereoffor all input points. The values are compared with a threshold θ1 in thethreshold data 23 in the memory device 20, and the input points aredivided into groups by collecting points within the threshold θ1 (S202).After S202, it is determined whether or not there exists a point group(S203). If there is no point group (S203: NO), the CPU 10 terminates thecurrent process and displays the result on the display apparatus 50. Ifthere is at least one point group (S203: YES), the CPU 10 detects apolygon that includes all points of the point group at a minimum area(S204) among prepared polygons in advance. Fundamental shapes of thepolygons in use here, which are concave or convex polygons, areprescribed in advance, and the polygons are stored as the polygon data22 in the memory device 20. For instance, the convex polygons have arectangular shape, a diamond shape, a regular octagonal shape, and soon, and the concave polygons are L-shaped, U-shaped, T-shaped,cross-shaped and so on. The CPU 10 assigns these concave or convexpolygons for each point group of at least one point (S204), and theouter shape and the rooftop shape of the three-dimensional structure aredetermined (S205).

[0053] Here, when the CPU 10 detects a concave or convex polygon thatincludes points at a minimum area, the CPU 10 needs to determinearrangement (orientation) of each of the prepared convex or concavepolygons through such an optimal angle thereof at which the polygon hasthe minimum area.

[0054] A description will now be given, with reference to a drawing, ofa method for finding the optimal arrangement (angle).

[0055]FIG. 3 shows an example of the method for determining arrangementof a polygon that includes points at a minimum area.

[0056] In FIG. 3, a rectangle (convex polygon) is used as one of thepolygons. The CPU 10 rotates the rectangle in contact with pointscounterclockwise bit by bit. The CPU 10 computes the area of therectangle that includes all the points and then determines a position ofthe rectangle where the rectangle has the minimum area. Similarly, theCPU 10 computes a minimum area for each concave or convex polygon suchas a pentagon and a U-shaped polygon in the polygon data 22. Finally,the CPU 10 selects the smallest polygon among the computed optimallyarranged polygons and determines an outer shape or a rooftop shape ofthe three-dimensional structure based on the shape of the smallestpolygon.

[0057] Although the rectangle is rotated counterclockwise in FIG. 3, thepresent invention is not limited to the counterclockwise rotation. Forinstance, the rectangle may be rotated clockwise. Alternatively, thepoint group may be rotated in a fixed state of the polygon.

[0058] A description will now be given, with reference to a drawing, ofthe second method for generating outer shapes and rooftop shapes.

[0059]FIG. 4 is a flowchart of a procedure for generating an outer shapeand a rooftop shape of a three-dimensional structure from point clouddata together with the corresponding building shape in a two-dimensionalelectronic map.

[0060] In FIG. 4, when the CPU 10 receives an execution instruction fromthe input device 40 in the same way as S201, the CPU 10 reads the pointcloud data 21 in the memory device 20 (S400). Then, the CPU 10 reads thetwo-dimensional electronic map data 25 from the memory device 20 anddivides the point cloud data into groups based on the correspondingbuilding shapes in the two-dimensional electronic map data 25 (S401).The CPU 10 further groups points in the point groups divided at stepS401 based on a threshold θ2 in the threshold data 23 (S402). Then, theCPU 10 determines whether or not there is a grouped point group (S403).If there is no such a point group (S403: NO), the CPU 10 sets thetwo-dimensional electronic map data 25 as an outer shape of thethree-dimensional structure (S407) and determines the outer shape andthe rooftop shape of the three-dimensional structure (S404). On theother hand, if there is at least one point group (S403: YES), the CPU 10detects a polygon that includes the points at a minimum area for eachpoint group (S405).

[0061] Here, when areas of the concave or convex polygons including thepoint group are computed and the minimum-size polygon is detected, it ispossible to use the two-dimensional electronic map data 25 to obtain thedirection of a building shape located at the same position as the pointgroup as a direction vector and narrow positions of the polygons (anglesand directions) by matching the direction vector with edges of thepolygons. As a result, if the two-dimensional electronic map data 25 areused, it is unnecessary to rotate the polygons bit by bit as describedwith reference to FIG. 3 so as to determine such positions thereof atwhich the areas are minimized. Thus, it is possible to reduce processingtime.

[0062] Then, the CPU 10 compares the determined polygon that includesthe points at the minimum area with the corresponding building shape inthe two-dimensional electronic map data 25 and arranges the outer shapeof the polygon by removing an overflow of the determined polygon fromthe building shape in the two-dimensional electronic map data 25 suchthat the polygon is included in the building shape in thetwo-dimensional electronic map (S406). After that, the CPU 10 determinesthe outer shape and the rooftop shape of the three-dimensional structure(S404). As a result, it is possible to generate the outer shape or therooftop shape of the three-dimensional structure with high accuracy.

[0063] According to execution of the above-mentioned procedures in FIG.2 and FIG. 4, it is possible to determine the outer shape and therooftop shape, two of the three items constituting the three-dimensionalstructure: the outer shape, the rooftop shape and the roof shape.

[0064] A description will now be given, with reference to a drawing, ofan algorithm for automatically generating a roof shape.

[0065]FIG. 5 is a flowchart of a procedure for generating a roof shapeof a three-dimensional structure from a point group.

[0066] In FIG. 5, the CPU 10 receives point groups obtained at step S202or step S402 (S501). Then, the CPU 10 uses functions (power seriesfunctions whose order is more than or equal to the first order or linearcombination functions of elementary functions such as trigonometricfunctions or exponential functions) in the function data 24 in thememory device 20 to compute such a function that differences betweenindividual heights z (z>0) and function values are minimized inaccordance with the least squares method. Here, the power seriesfunctions are series formulated by multiplying a number or a characterseveral times, and the least squares method is a method for determiningsuch a line (curve) that a sum of squares of differences between theline (curve) and individual points, that is, an area of differencesbetween the line (curve) and individual points, is minimized.

[0067] In FIG. 5, a second-order power series function(z=ax²+by²+cxy+dx+ey+f) is examined as a function to be determined inaccordance with the least squares method. In this example, the sixcoefficients: a, b, c, d, e and f are determined in accordance with theleast squares method (x and y are variables).

[0068] The CPU 10 computes an error between the height z of the powerseries function and the height of a point (S502), and it is determinedwhether or not the error is less than or equal to a threshold θ3 in thethreshold data 23 (S503). If the error is less than or equal to thethreshold θ3 (S503: YES), the CPU 10 proceeds to a determination step ofa roof shape. In the roof shape determination step, the roof shape isdetermined among a plurality of roof shapes based on the determinedcoefficients (a, b, c, d, e and f). Here, the plural roof shapes arestored in the roof shape data 26 in the memory device 20. FIG. 6 is adiagram illustrating an example of roof shapes and names thereof.

[0069] In FIG. 5, for instance, if the coefficients a, b and c areapproximately equal to 0 (S504: YES) and further the coefficients d ande are approximately equal to 0 (S505: YES), the CPU 10 determines theroof shape as “roku-roof”. On the other hand, if the coefficient d or eis not approximately equal to 0 (S505: NO), the CPU 10 determines theroof shape as “katanagare-roof”. In FIG. 5, the notation “˜” representsapproximation. For instance, the notation “a˜0” represents that thecoefficient a is approximately equal to 0, and the notation “a˜b”represents that the coefficient a is approximately equal to b.

[0070] At step S504, if at least one of the coefficients a, b and c isnot approximately equal to 0 (S504: NO), the coefficient a isapproximately equal to the coefficient b, and the coefficient c isapproximately equal to 0 (S506: YES), the CPU 10 determines the roofshape as “dome-roof”.

[0071] Here, if the coefficient a is not approximately equal to thecoefficient b or the coefficient c is not approximately equal to 0(S506: NO), the CPU 10 determines the roof shape based on an edgethereof. Namely, when the roof has the edge as in the “kirizuma-roof”,“yosemune-roof” and “maneki-roof” (ref. FIG. 6), the CPU 10 extractspoints located at higher positions (points of large z values) from thepoint group so as to determine the roof shape. Based on the extractedpoints, the CPU 10 determines the edge from functions (lines or curves)in the function data 24 in accordance with the least squares method(S507). Then, the CPU 10 computes errors between the extracted pointsand the function values and then finds coefficients of the function(S508), and it is determined whether or not the errors are less than orequal to a threshold θ4 (S509). Additionally, the CPU 10 determines theroof shape in comparison with the computed coefficients.

[0072] A description will now be given, with reference to drawings, of aprocess flow for determining an edge from a point group.

[0073] From points in the point group as shown in FIG. 7A, the CPU 10extracts points located at higher positions as shown in FIG. 7B. The CPU10 determines a line (curve) in accordance with the least squares methodsuch that errors between the extracted points at high positions andvalues of a predetermined function are minimized, and the line (curve)is determined as the edge (FIG. 7C).

[0074] At step S509, if the error is less than or equal to the thresholdθ4 (S509: YES), it is determined whether or not the value “c²” isapproximately equal to the value “4ab” (S510). If the value “c²” isapproximately equal to the value “4ab” (S510: YES), the roof shape isdetermined as a “kirizuma-roof”. In contrast, if the value “c²” is notapproximately equal to the value “4ab” at step S510 (S510: NO) andfurther the coefficients d and e are approximately equal to 0 (S511:YES), the roof shape is determined as a “yosemune-roof”. Here, if thecoefficient d or e is not approximately equal to 0 (S511: NO), the roofshape is determined as a “maneki-roof”.

[0075] At step S509, if the error is not less than or equal to thethreshold θ4 (S509: NO), it is determined whether or not the value “c²”is approximately equal to the value “4ab” (S512). If the value “c²” isapproximately equal to the value “4ab” (S512: YES), the roof shape isdetermined as a “kamaboko-roof” or a “koshiore-roof”. In contrast, ifthe value “c²” is not approximately equal to the value “4ab” (S512: NO)or if the error is not less than or equal to the threshold θ3 (S503:NO), the roof shape is determined as “others” and is arbitrarily set.According to the above-mentioned procedure, it is possible toautomatically generate the roof shapes of three-dimensional structuresof uniform quality. Here, the automatic roof shape generation algorithmshown in FIG. 5 is not limited to the above-mentioned procedure, andvariations thereof can be made corresponding to comparison contents offunctions in use and coefficients thereof.

[0076] The CPU 10 supplies the obtained three-dimensional structure dataof the outer shape, the rooftop shape and the roof shape generated tothe output device 60, and then the process result is displayed on thedisplay device 50.

[0077] According to the present invention, by using onlythree-dimensional point cloud data having height information thereof orusing building shapes in a two-dimensional electronic map together withthe point cloud data, it is possible to automatically generate shapes ofthree-dimensional structures of uniform quality at a reasonable cost.

[0078] It is noted that programs according to the present invention areexecutable in arbitrary terminals by storing the programs in a portablerecording medium such as a CD-ROM (Compact Disk Read Only Memory) and afloppy disk.

[0079]FIG. 8 shows an example of a three-dimensional structure generatedaccording to the present invention.

[0080] The three-dimensional structure in FIG. 8 is generated in such away that an outer shape thereof is determined based on the proceduredescribed with reference to FIG. 2 and a rooftop shape thereof isdetermined by setting the average of points in a point group as a heightthereof.

[0081] Additionally, FIG. 9 shows a second example of thethree-dimensional structure generated according to the presentinvention.

[0082] The three-dimensional structure in FIG. 9 has an outer shape, arooftop shape and a roof shape that are determined based on theprocedures with reference to FIG. 4 and FIG. 5. In FIG. 9, the“kirizuma-roof” is automatically generated as the roof shape thereof.

[0083]FIG. 10A shows point cloud data in a block (1 km²) in Tokyoobtained with a laser profiler, and FIG. 10B shows an example ofthree-dimensional structures generated from the point cloud data in FIG.10A in accordance with the present invention. Although there are about4000 buildings in this block, it is possible to generate all thethree-dimensional structures in about 30 minutes in accordance with theautomatic three-dimensional structure shape generation method accordingto the present invention (by using one computer with an 800 MHzPentium(R) III CPU). Additionally, it is possible to suppress qualitydifferences with respect to the generated three-dimensional structureshapes.

[0084] Consequently, for instance, if the automatic three-dimensionalstructure generation method is applied to all of the 23 wards in Tokyo,it takes only about 300 hours (about 12 days) to process data thereof.Furthermore, since the automatic three-dimensional structure generationmethod can be executed for each block (point cloud data region)separately, it is possible to reduce computation time thereofcorresponding to the number of computers in use. Additionally, if futureperformance improvement of computers is taken into account, it ispossible to expect further reduction of the computation time.

[0085] As mentioned above, according to the present invention, it ispossible to automatically generate shapes of three-dimensionalstructures of uniform quality at a reasonable cost.

[0086] The present invention is not limited to the specificallydisclosed embodiments, and variations and modifications may be madewithout departing from the scope of the present invention.

1. An automatic three-dimensional structure shape generation apparatusfor automatically generating a shape of a three-dimensional structurefrom a plurality of points having three-dimensional coordinatescontaining height information, comprising: means for constituting apoint group by collecting such points that three-dimensional distancesbetween said points are within a predetermined threshold ortwo-dimensional distances and height differences between said points arewithin predetermined thresholds; means for detecting a polygon thatincludes the points of the point group at a minimum area from at leastone of a plurality of predetermined polygons; and means for generatingone of an outer shape and a rooftop shape of the three-dimensionalstructure based on said detected polygon having the minimum area.
 2. Theautomatic three-dimensional structure shape generation apparatus asclaimed in claim 1, wherein said means for detecting the polygon havingthe minimum area gradually rotate one of all points of said point groupand at least one of the predetermined polygons by a unit of apredetermined angle so as to find an angle at which said polygon has aminimum area.
 3. The automatic three-dimensional structure shapegeneration apparatus as claimed in one of claim 1 and claim 2, whereinsaid means for detecting the polygon having the minimum area detect thepolygon that includes the points of the point group at the minimum areabased on an angle at which an edge of said polygon that includes thepoint group coincides with a predetermined direction vector.
 4. Theautomatic three-dimensional structure shape generation apparatus asclaimed in one of claim 1 through claim 3, further comprising one ofmeans for removing an overflow portion of one of the generated outershape and the generated rooftop shape of the three-dimensional structurefrom a corresponding building shape in a two-dimensional electronic mapand means for arranging one of the generated outer shape and thegenerated rooftop shape of the three-dimensional structure such thatsaid generated one is included in said corresponding building shape inthe two-dimensional electronic map.
 5. An automatic three-dimensionalstructure shape generation apparatus for automatically generating ashape of a three-dimensional structure from a plurality of points havingthree-dimensional coordinates containing height information, comprising:means for constituting a point group by collecting such points thatthree-dimensional distances between said points are within apredetermined threshold or two-dimensional distances and heightdifferences between said points are within predetermined thresholds;means for using height information z (z>0) of the points of the pointgroup and a predetermined function to determine a coefficient of saidfunction such that errors between said points and said function areminimized; and means for generating the shape of the three-dimensionalstructure based on said coefficient.
 6. The automatic three-dimensionalstructure shape generation apparatus as claimed in claim 5, wherein saidmeans for generating the shape of the three-dimensional structure basedon the coefficient compute at least one coefficient of one of a powerseries function whose order is higher than or equal to a first order anda linear combination function of an elementary function in accordancewith a least square method, and generate a roof shape of thethree-dimensional structure based on a size relation of said at leastone coefficient.
 7. The automatic three-dimensional structure shapegeneration apparatus as claimed in claim 5, wherein said means forgenerating the shape of the three-dimensional structure based on thecoefficient extract a plurality of points, which are located at higherpositions, from the point group, find one of a line and a curve suchthat errors between said plural points located at higher positions andsaid one are minimized, and generate a roof shape by determining saidone as a roof edge.
 8. An automatic three-dimensional structure shapegeneration method for automatically generating a shape of athree-dimensional structure from a plurality of points havingthree-dimensional coordinates containing height information, theautomatic three-dimensional structure shape generation method comprisingthe steps of: constituting a point group by collecting such points thatthree-dimensional distances between said points are within apredetermined threshold or two-dimensional distances and heightdifferences between said points are within predetermined thresholds;detecting a polygon that includes the points of the point group at aminimum area from at least one of a plurality of predetermined polygons;and generating one of an outer shape and a rooftop shape of thethree-dimensional structure based on said polygon having the minimumarea.
 9. The automatic three-dimensional structure shape generationmethod as claimed in claim 8, wherein said step of detecting the polygonhaving the minimum area gradually rotates one of all points of saidpoint group and at least one of the predetermined polygons by a unit ofa predetermined angle so as to find an angle at which said polygon has aminimum area.
 10. The automatic three-dimensional structure shapegeneration method as claimed in one of claim 8 and claim 9, wherein saidstep of detecting the polygon having the minimum area detects thepolygon that includes the points of the point group at the minimum areabased on an angle at which an edge of said polygon that includes thepoint group coincides with a predetermined direction vector.
 11. Theautomatic three-dimensional structure shape generation method as claimedin one of claim 8 through claim 10, further comprising one of a step ofremoving an overflow portion of one of the generated outer shape and thegenerated rooftop shape of the three-dimensional structure based on acorresponding building shape in a two-dimensional electronic map and astep of arranging one of the generated outer shape and the generatedrooftop shape of the three-dimensional structure such that saidgenerated one is included in said corresponding building shape in thetwo-dimensional electronic map.
 12. An automatic three-dimensionalstructure shape generation method for automatically generating a shapeof a three-dimensional structure from a plurality of points havingthree-dimensional coordinates containing height information, theautomatic three-dimensional structure shape generation method comprisingthe steps of: constituting a point group by collecting such points thatthree-dimensional distances between said points are within apredetermined threshold or two-dimensional distances and heightdifferences between said points are within predetermined thresholds;using height information z (z>0) of the points of the point group and apredetermined function to determine a coefficient of said function suchthat errors between said points and said function are minimized; andgenerating the shape of the three-dimensional structure based on saidcoefficient.
 13. The automatic three-dimensional structure shapegeneration method as claimed in claim 12, wherein said step ofgenerating the shape of the three-dimensional structure based on thecoefficient computes at least one coefficient of one of a power seriesfunction whose order is higher than or equal to a first order and alinear combination function of an elementary function in accordance witha least square method, and generates a roof shape of thethree-dimensional structure based on a size relation of said at leastone coefficient.
 14. The automatic three-dimensional-structure shapegeneration method as claimed in claim 12, wherein said step ofgenerating the shape of the three-dimensional structure based on thecoefficient extracts a plurality of points, which are located at higherpositions, from the point group, finds one of a line and a curve suchthat errors between said plural points located at higher positions andsaid one are minimized, and generates a roof shape by determining saidone as a roof edge.
 15. A program for causing a computer toautomatically generate a shape of a three-dimensional structure from aplurality of points having three-dimensional coordinates containingheight information, comprising the steps of: constituting a point groupby collecting such points that three-dimensional distances between saidpoints are within a predetermined threshold or two-dimensional distancesand height differences between said points are within predeterminedthresholds; detecting a polygon that includes the points of the pointgroup at a minimum area from at least one of a plurality ofpredetermined polygons; and generating one of an outer shape and arooftop shape of the three-dimensional structure based on said detectedpolygon having the minimum area.
 16. The program as claimed in claim 15,wherein said step of detecting the polygon having the minimum areagradually rotates one of all points of said point group and at least oneof the predetermined polygons by a unit of a predetermined angle so asto find an angle at which said polygon has a minimum area.
 17. Theprogram as claimed in one of claim 15 and claim 16, wherein said step ofdetecting the polygon having the minimum area detects the polygon thatincludes the points in the point group at the minimum area based on anangle at which an edge of said polygon that includes the point groupcoincides with a predetermined direction vector.
 18. The program asclaimed in one of claim 15 through claim 17, further comprising one of astep of removing an overflow portion of one of the generated outer shapeand the generated rooftop shape of the three-dimensional structure froma corresponding building shape in a two-dimensional electronic map and astep of arranging one of the generated outer shape and the generatedrooftop shape of the three-dimensional structure such that saidgenerated one is included in said corresponding building shape in thetwo-dimensional electronic map.
 19. A program for causing a computer toautomatically generate a shape of a three-dimensional structure from aplurality of points having three-dimensional coordinates containingheight information, comprising the steps of: constituting a point groupby collecting such points that three-dimensional distances between saidpoints are within a predetermined threshold or two-dimensional distancesand height differences between said points are within predeterminedthresholds; using height information z (z>0) of the points of the pointgroup and a predetermined function to determine a coefficient of saidfunction such that errors between said points and said function areminimized; and generating the shape of the three-dimensional structurebased on said coefficient.
 20. The program as claimed in claim 19,wherein said step of generating the shape of the three-dimensionalstructure based on the coefficient computes at least one coefficient ofone of a power series function whose order is higher than or equal to afirst order and a linear combination function of an elementary functionin accordance with a least square method, and generates a roof shape ofthe three-dimensional structure based on a size relation of said atleast one coefficient.
 21. The program as claimed in claim 19, whereinsaid step of generating the shape of the three-dimensional structurebased on the coefficient extracts a plurality of points, which arelocated at higher positions, from the point group, finds one of a lineand a curve such that errors between said plural points located athigher positions and said one are minimized, and generates a roof shapeby determining said one as a roof edge.
 22. A recording medium forrecording the program as claimed in one of claim 15 through claim 21.